| Poly(phthalazinone ether sulfone ketone) is a kind of high-performance material with high glass-transition temperature, good solubility, well membrane-forming ability, good mechanical performance and chemical resistance. An excellent rejection and pure water flux can be obtained form the membrane prepared with PPESK. But with further experiment, a disadvantage was discovered for when the membrane prepared from it was dried, the membrane will become brittle, witch will has a strong influence on the production of commercial modules. On the purpose to reduce or eliminate the problem, experiment was carried out to pick up kinds of material with a good mechanical property and more important, the one will be miscible with PPESK. And more, blend membrane is prepared. Further more, properties and morphology of the blend membrane are measured.Hansen's solubility parameters are introduced to select membrane materials which have similar values with the value of PPESK. The selected are dissolved in solvent with PPESK that has a weight ratio of 50:50, to measure if they are miscible. Then, miscible ones are picked to produce membrane for further experiment. The miscibility of blend are characterized by other ways, such as by blending the two materials to see if they are miscible, by measure the Tg of the blend, and also by measuring the absolute viscosity of the blend to ensure if the viscosity-blend ratio relation is linear and also FT-IR. At last, poly ether imide was found has a good mechanical property and miscible with PPESK.Blend membrane are prepared though L-S phase separation. Experiment goes further to prepare membrane from the blend with blend ratio, the result shows that there is a strong influence of the blend ratio on the mechanical and separation properties. As the PPESK/PEI blend ratio changed form 20/80 to 80/20, the pure water flux of the membrane sharply increased from 19L·m-2·h-1 to 380L·m-2·h-1 with a higher rejection of PEG10000. The results also showed us there is a minimum of the blend with the PPESK/PEI ratio is 80/20, and with the further increase of PEI ratio in the blend, the tensile strength and flexibility increased. The data showed that the comprehensive property of the membrane climb up to the max when the blend ratio of PPESK/PEI is 40/60.Total polymer concentration and additive on the performance of the blend membrane is also examined. The result shows that with the increase of total polymer concentration, the pure water flux will decrease and the rejection increase accordingly. High performance membrane can be obtained when the total polymer concentration is between 15% and 16%.The additive give a complicated influence on the performance of the membrane, but a common rule is found that when the approaching ratio of different additive in the casting solution is between 0.4 and 0.6, a high performance membrane can be obtained. With further experiment it was found that the addition of Poly ethyl glycol has a molecular weight no more than 800, high performance membranes can always be obtained.The operate process in preparing the blend membrane also has an obvious influence on the performance of the membrane prepared. The influence of coagulation temperature, coagulation composition, evaporation temperature, evaporation time, and humid on the properties of blend membrane are measured, the results shows that as the increase of coagulation temperature and the increase of NMP in the coagulation composition, the pure water flux increase and the retention of PEG10000 decrease;as the higher the evaporation temperature and the longer the evaporation time, the pure water flux decrease and the retention increase;as the increase of humidity, the pure water flux decrease and the retention increase.SPPESK is introduced and used to blend with PPESK/PEI blend, on the purpose to studying the effect of SPPESK on the SPPESK/PPESK/PEI blend membrane. The result showes that the addition of SPPESK strongly increases the pure water flux of tri-blend membrane and has a little decrease in the retention. Additives give a strong influence on the properties of the blend membrane. With the increase of the additive in dope solution, the pure water flux has a sharp increase as the retention keeps at a high level. |
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